soong: use optimal FPU for Cortex-A7

* Cortex-A7 supports VFPv4 instructions

Test: make otapackage
Change-Id: I709811980cda398994ba8c6e791a8625a3422455

cc/config/arm_device.go

@@ -109,6 +109,7 @@ var (
 		},
 		"cortex-a7": []string{
 			"-mcpu=cortex-a7",
+			"-mfpu=neon-vfpv4",
 			// Fake an ARM compiler flag as these processors support LPAE which GCC/clang
 			// don't advertise.
 			// TODO This is a hack and we need to add it for each processor that supports LPAE until some